Flash lamp attachments are widely used with cameras of various types to provide sufficient illumination in low light conditions to match the exposure characteristics of the film used in the camera. Standard cameras, such as the popular 35MM cameras, generally have a flash attachment "shoe" in the form of a conductive bayonet plate fitting on the top of the camera. Different types of flash guns, or flash lamp devices, are mounted on this shoe with a mating bayonet fitting. These fittings are standardized, and the camera fitting is connected with the shutter mechanism of the camera to complete an electrical circuit upon the tripping or release of the shutter. Completion of this electrical circuit then is used in the flash gun itself to complete a circuit through a battery power supply to the flash lamp. The flash lamp may be in the form of a flash bulb, which is consumed when it is triggered, or it may be an electronic flash which is capable of a large number of repeated operations before it needs replacement.
For taking pictures in dim light conditions, the lens opening of the camera is adjusted in accordance with the film speed parameters and the characteristics of the flash lamp. Typically, when a camera is used for taking flash pictures, a single shutter speed (such as 1/60th of a second) is employed, and adjustments are made in the lens opening for establishing the correct amount of exposure for the film when the subject is at different distances from the camera. Only a single flash lamp is provided in the flash gun unit, and the unit itself usually has a chart on the back panel which enables the user to correlate the film speed, distance from subject, and the camera lens opening for the proper exposure. In some professional applications, satellite flash units located at a distance from the one on the camera are used to supplement the light from the camera and to provide light from different angles. Such satellite units include sensors which cause them to be triggered by the light from the primary flash unit on the camera. This results in nearly instantaneous triggering of all of the flash units to provide the desired lighting.
Infrared film has been developed for 35MM cameras to permit them to be used in extremely low light conditions to detect infrared radiation from objects to be photographed. Such film typically has a primary infrared frequency of response. The camera may be equipped with a filter to pass frequencies of light in the infrared region and a block out light frequencies in the visible region to insure proper exposure of the film and to eliminate undesirable effects which could be caused by visible light leakage. Infrared film, however, is limited in its applications to photographing objects which emit radiation at the infrared frequencies corresponding to the sensitivity or response characteristics of the film. Consequently, applications for photographing objects with such infrared film have been somewhat limited.
It is desirable to provide a device which permits a camera to be used with infrared film for photographing objects in low infrared light conditions even when the objects do not naturally radiate infrared signals in the spectrum of sensitivity of the film. It is desirable to provide a unit which is simple in operation, relatively inexpensive in cost and which is versatile for accomplishing this purpose.